Quick guide to SSH keys

To simplify remote logins you can use ssh keys. Information is stored below "$HOME/.ssh". Starting from scratch on a system execute the command:
  ssh-keygen -t rsa

This generates a public/private key set. You do this once on a system from which you will want to provide authentication. You will normally choose the default directory. If a pass-phrase is used you need to enter that pass-phrase at least once on the machine requesting authentication. See "ssh-agent" man page for information about keeping an authentication key in memory. If you do not use a pass-phrase things are a bit simpler at the expense of security.

The ssh-keygen command creates files:
  .ssh/id_rsa
  .ssh/id_rsa.pub

You will copy the .ssh/id_rsa.pub key to another machine. This file can copied as:
  scp -p .ssh/id_rsa.pub remotesys:.ssh/authorized_keys

If you wish to grant multiple systems remote access you need to cut/paste the id_rsa.pub file from the machine which executed ssh-keygen such that multiple entries are placed in the authorized_keys file.  Place entries one per line. You can also append the entry like so:
  cat ~/.ssh/id_rsa.pub | ssh -l userid hostname "cat - >>.ssh/authorized_keys"

The .ssh directory must have permission 700.